Random thoughts on resource management in RTS

Strategy games, especially those in the Real Time Strategy genre, tend to follow a common formula. In each match, the players start with limited resources: typically, a single “command center” structure and a handful of scouting or economy-focused units, depending on the systems the game uses for resource gathering. From there, players will typically mine, build, research and produce resources, structures, upgrades and units respectively, making choices that influence the growth of their economy, the raw power and abilities of individual entities within their force, and the size of their force. This, in concert with information about their opponent’s relative economy and troop strength, will inform the decisions they make to attack, defend, produce, posture, harass, etc.

The ‘average’ RTS, if there is such a thing, is designed with the intent of forcing the player to prioritize the allocation of scarce resources. These resources can be explicit or implicit. Explicit resources are those gathered via some mechanism within the match – gold is mined, Fuel is generated from capturing points on the map, Energy is a factor of how many power plants you have produced vs how much power your buildings consume et cetera. Even unit ability cooldowns represent a sort of renewable resource. Implicit resources are limiting factors such as a player’s time and attention, force concentration and any game mechanic which enables or restricts player actions in pursuit of the match goal.

Please, bear with me as I explore in my own rambling way some considerations on RTS resource systems and try to shed some light on variants that I feel have had far too little thought put into them. I look forward to any and all comments on the subject.

The Basics

I’ll be quite up front here – I do not pretend that this is a researched, academic dissertation. I wouldn’t really know where to start with such an endeavor. Fortunately, the good people of twitter (especially the estimable @apgamesdev, have linked me to some articles like this one or this one that cover the topic in alternate and perhaps better ways. Feel free to correct me at your leisure!

At their core, resource systems in real-time strategy games exist to control player choice. Almost every real-time strategy title is built on top of a system of progression from low cost, low power combatants (be they abstracted to chess-like game pieces or attempts at accurately representing WW2 Volksgrenadiers, or something else entirely) to more interesting, powerful, specialized and typically rare weapons of war. Very few RTS games buck this trend by, for instance, starting one or both players off with pre-existing armies or allowing access to the heaviest hitters either first or in the early game. Resources, and time which I consider to be an implicit resource, are the vehicles with which players navigate the web of choices presented to them by a given game to complete that game’s objective.

Effectively, “resources” are a system of agency for the player. With resources, a player accumulates available options and is given agency to act and react to the evolving systems and conditions of the game. Take a card game like Magic: The Gathering for example. As a player plays Land cards, they gain a renewable resource which they can expend to play creature, spell and artifact cards. Without the limiting influence of Land cards, powerful and therefore rare cards that produce profound effects on the game would be just as available as common creature cards that have limited effects. Land exists as a way to limit the speed with which players are able to access the most powerful cards, and put a hard limit on a player’s ability to act at any given time. Players can only ‘tap’ the amount of Land cards they have – if they have 5 Land cards, they can only deploy 5 Land worth of spells and effects on their turn (barring of course any special rules).

A strategy game without resources would effectively be a game without consequence. It would be as if chess pieces re-entered play every time they are captured, or if Magic the Gathering players could play any card in their entire deck without worrying about the size of the hand, Land cost of the card etc. Resources do much to impart a gravitas or consequence to a game, and infuse a need for efficiency in every part of a game. This exists in a way in any strategy game that allows ‘infinite resources’ and ‘instant build option’ cheat codes. I only reference this here as a sort of thought experiment – strategy games could be built to account for not having a resource system, but I think they’d tend to produce ultimately unsatisfying results. Even tabletop wargames like Warhammer have a resource system of types that limit the player’s army to a certain number of ‘points’ and restrict action based on number of actions a turn.

Multiple Resources

I won’t go much into multiple resource games. Oxeye games studios has an excellent breakdown on the effects of multiple resource systems here. I admit that I don’t have a terribly strong grasp of specifically how a multiple resource system plays into a game’s mechanics beyond the obvious – one resource is typically more scarce than the other and therefore more valuable. Often, this resource is used for more advanced applications – research, high powered units, etc. Sometimes, 3 or more resources are introduced either with various applications, like Company of Heroes global Munitions resource which players spend to activate most unit abilities, or to increase focus on economy, like Age of Empires Wood, Gold, Food and Stone that put pressure on construction of towers, fortresses and high level units, as well as controlling the pace at which a player is able to move through the Ages of the game.

Time as a Resource

So, now that we have a handle on the purpose of resources within an RTS game (to state again, it’s to control rate at which a player opens up play options, to put a limit on more powerful elements under the player’s control, and to provide a need for efficiency and judgment in user actions) let’s delve a little deeper into the concept.

The player themselves have a limited supply of an implicit resource – time. Any well designed RTS game will take into account the number of actions, and indeed perhaps more importantly the number and difficulty of each decision that a player will be forced to make within a given window in which to be effective.

The entire concept of the ‘build order’ is a by-product of resources and time. In the early stages of the game, the player often has far more options than they can afford to pursue. Do they spend resources on additional resource generation capabilities, ‘booming’ their economy to a late game advantage? Do they spend more resources on units, to ‘rush’ over to the enemy’s base? When is it appropriate to make the expenditure of upgrading to more powerful units versus acquiring additional resource generation capabilities versus acquiring additional unit production capabilities?

StarCraft and StarCraft 2 are perhaps the most mechanically demanding RTS games currently being played. These games are designed to respond about as quickly as the user is able to input commands. Most other RTS games intentionally or unintentionally put an effective cap on the number of actions the player can take in a given time window. Either way, the player’s time and attention are effectively resources themselves that must be spent managing a game’s economy and the player’s army.

In other RTS games, units have an effective ‘time cost’ to perform actions. Tanks in Company of Heroes cannot be given orders too regularly as the refire rate on their main guns often approaches 6-10 seconds, and their pathing can be confounded by excessive repeat orders. Air units in Command and Conquer games have temporal limits on their viability as well, as they must take the time to fly back to launch pads to restock their ammo supplies after each volley. In Supreme Commander, the very position of a player’s army has a ‘time cost’ as map size is so large in comparison to unit movement rate that being caught out of location requires a non-trivial resource investment to correct.

Like any other resource, either player is capable of forcing their opponent to misallocate or waste time to their own advantage. Indecision, fear and distraction are powerful tools.

Some games like Dawn of War: Dark Crusade (the Necrons faction), Z by the Bitmap Brothers, and Command and Conquer 4 literally use time as their primary resource, or the primary resource of a single faction. In these instances, cooldowns or training time are the primary delimiting factor in unit production. It’s an interesting alternative to traditional resource costs, for sure.

Examples + Thoughts

Though the basic formula described above holds more or less true for the majority of RTS games, across the breadth of the genre there are several unique models that I’d like to explore briefly in an effort to set up a baseline for my discussion of alternative methods. Let’s start with some of the big names.)

StarCraft 2

StarCraft’s resource system is very close to the RTS baseline. At its core are workers (SCVs, Probes and Drones) which serve both as the means of constructing new buildings and collecting the game’s 2 resources. Over the course of a match, dozens of these units are created to mine minerals and gas at the player’s bases, which tend to center around the Command Center that serves as a resource drop-off point. During a match of any decent length, 80-90 of the 200 population cap will be involved in resource gathering during the game’s peak, nigh half of the units involved.

The game has 2 main resources. The more plentiful of the two, Minerals, are involved in all building, unit and upgrade production. The more scarce resource, Vespene Gas, is mostly a factor of the power or versatility of the unit or upgrade being utilized. Spellcaster units, which have some of the highest potential impact on the game, also tend to cost the most Vespene. Some assault units like the Archon are also comparatively expensive. Spellcaster units have their own resource, energy, which limits the usage of their abilities over a given time frame.

The issue, for me, with this system and the systems of games like it is twofold. First, it ties victory in the match fairly closely to production. As you’ll see, other resource systems exist which separate the condition of victory out as a separate resource, and which produce interesting effects on the game’s combat system absent here. Units are spent resources, produced from facilities that exist as spent resources – many of the potential benefits of those resources has been resolved already. StarCraft and other RTS games like it cause spent resources to become a specific set of options: these unit types can be produced at this frequency, these purchased units have these other effects. StarCraft puts the efficacy of that potential largely in the hands of the player, however, with increased unit control and game awareness able to increase the relative value of those units many fold. There are pros and cons here, of course.

StarCraft puts an emphasis on efficiency and control of units, called tactics in the parlance of genre insiders, specifically because of the way its resource system locks up the potential of spent resources. There’s no buy-back system for units or structures, and the best ways to win center around finding ways to increase the value of your resources relative to that of your opponent.

Company of Heroes 2

Company of Heroes has a completely different approach to resource management. In COH2, the base resource for purchasing units, Manpower, is generated at a rate based on the number of units the player has. The more units, the slower Manpower accumulates. This is in some ways similar to the WarCraft 3 mechanic of “upkeep.”

The other 2 resources, Fuel and Munitions, control the purchase of more powerful assets (like upgrading unit abilities or calling in tanks) and serve as a common source of funding for all potential unit abilities. Company of Heroes has no economic units such as the StarCraft SCV – it has no call for them. All infantry can capture points of any type.

Both Fuel and Munitions are generated by points spread out across the map. Players are forced to spread their forces out across the entire map from the beginning of the game to maintain resource flow parity with their opponent. Since Munitions are pulled from a common pool, any unit ability has an impact on all other units potential to call in their own abilities. This makes Munitions management an interesting mechanic, especially in the early game when Munitions are more scarce. Fuel, in its turn, limits the amount of Manpower that can be spent on game changing assets like tanks.

The resource design of Company of Heroes dictates (at least in 1v1 matches) a more spread out conflict. The mechanical design encourages diverse forces, as unlike StarCraft, certain unit or weapon types are absolutely required to even damage other unit types.

Winning the game is itself a resource in Company of Heroes. Players begin the pool with a pool of Victory points that are decreased when the player’s opponent captures more Victory sectors on the map. The player whose points are decreased to 0 loses. This at least partially divorces winning from resource efficiency. While it is unlikely that a player whose forces in the game are significantly weaker can still win, it’s possible to hold onto the Victory sectors long enough to achieve the win state of the game even after suffering heavy losses. I’ll talk more about the slippery slope and player combacks in a future article – it’s too dense a subject to cover here.

Wargame Series

Wargame, though it portrays itself as an “RTS” is actually a real-time tactics game. It features absolutely no base building or resource gathering in the traditional sense. Units are acquired via a points system much like the one from Warhammer. A substantial portion of a player’s total available unit capacity is deployed right off the bat, with additional resources to purchase subsequent units added at a rate determined by the number of zones the player controls. Players begin the game with more units than they’ll be able to call into combat over the rest of the match.

The real resources in Wargame are fuel and ammunition. Every unit that has weapons has a finite ammo capacity for those weapons – tanks have ammo for their main gun, for and MG they have mounted, and for any AA system they have mounted. When they run out of ammo, they become liabilities – utterly useless in combat until they are respplied. Likewise, when they run out of fuel they are literally stuck in place until they are refueled. The resource system in this game punishes players for managing their units poorly. Concentrating a force in one area of the match’s game map is a decision based on an actual in game resource – a tank does probably not have enough fuel to cross the map without being resupplied. Combat engagements can stall out as players’ units run out of ammo and must retreat to restock. A player’s offensive capabilities can be cut short by the destruction of their fleet of resupply trucks.

This system is beautiful to me. It’s eminently understandable and it has a profound effect on the game’s combat system. The fact that it exists in a game that otherwise seems to try its hardest to confound the player is extremely disappointing.

Alternate Systems

Ultimately, I feel like the concepts of ammunition-as-resource and time-as-resource are under explored in the RTS genre. Alternate resource system open up completely new mechanical realities in RTS games – in a game with fuel, for instance, a player could start a match with a supremely powerful unit capable of wiping out armies, but without agency to cross the map to their opponents infrastructure without first going through the process of ensuring it has a supporting logistical ability to cross the distance. Armies reliant on ammo, as in Earth 2150, can be crippled directly through harassment of ammo production capabilities, and battles can be dictated by logistical trains as easily as destroyed by high damage sources. The implications of logistics in army movement are profound in the RTS setting, and few games aside from Earth 2150 and Wargame have explored them.

6 thoughts

Looks like this is an older post but just read it. I love this discussion but how do you time as a resource in a game like World in Conflict where while you don’t control resources at all in the regular sense but instead it’s tied to time, if you lose a large percentage of your army, you are forced into a naturally defensive stance until you can recoup your units (which comes back faster the more you lose but slow down with minimal losses). I did find this created unique tactical decision making in game, if I lose most of my forces I can fall back to a position that favors me or I can move to another section of the map and counter and reinforce from this new location when my units are ready.

Would love to hear your thoughts on the WiC resource mechanic, if you view it as a resource in the first place.

I really appreciate systems similar to that in World in Conflict and think that it is a valid approach to resources in RTS and RTT games. Similarly the Necron faction in Dawn of War Dark Crusade utilized training time as its ‘resource’ and capturing resource nodes actually decreased the train time of that faction’s units.

In games like Supreme Commander and Planetary Annihilation, time is absolutely an actual resource, as you can increase the time efficiency of factories etc through adjacency bonuses.

As much as a resource in an RTS is a limiting factor in addition to being a reflection of player agency, time and even attention are valid resources. I do think that time is often best served as an implicit cost or resource amongst many, as resource systems tend to force the player to think and prioritize more than time alone